JPS6218703A - Metalized film capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement in a metallized film capacitor which is mainly used in electrical equipment and has a safety function in the event of dielectric breakdown by dividing a vapor-deposited metal electrode. .

BACKGROUND OF THE INVENTION In recent years, demands for safety have increased, and capacitors have come to have built-in safety devices.

This is intended to prevent smoke and fire from occurring when the capacitor malfunctions. Common safety devices utilize temperature rise and case deformation when capacitors break down.

Broadly speaking, safety devices can be divided into pressure mechanical cutoff type, current fuse type, and temperature fuse type.By incorporating safety devices, abnormal situations can be prevented, but this increases the capacitor volume, It cannot be said to be perfect from an economic point of view due to increased man-hours, high cost, etc.

Conventionally, in order to solve the above-mentioned problems, a capacitor has been proposed in which a divided electrode is provided so that the capacitor element itself has a safety function, as shown in FIG. 3, without providing a safety device.

(Japanese Unexamined Patent Publication No. 57-117226) In FIG. 3, 1 is a capacitor element, 2 is a segmented vapor deposited electrode film, 3 is a segment margin, 4 is a vapor deposited film removed area (blank area), and 6 is an undivided vapor deposited electrode. It's a film.

Problems to be Solved by the Invention However, in recent years, there has been an increasing demand for higher withstand voltages and higher potential gradients, and for use at voltages in the region where corona discharge occurs, it has become necessary to The breakdown voltage may decrease due to minute partial discharges (corona),
There was a problem in that the capacitor capacity at the end of its life decreased.

Therefore, it has been considered to increase the sheet resistance value of the metallized layers of both the two poles than before, but thinning the metallized layer improves self-healing performance and improves the initial capacitor breakdown voltage, but the aluminum metal layer As it becomes thinner, it tends to locally change to aluminum oxide, which has the disadvantage of increasing the capacitance decrease during its life, which was not suitable.

Furthermore, in the case of capacitors that have a split electrode structure and have a self-protection function, microscopic discharge (corona) may occur at the split portion of the split electrode, and a high potential gradient is applied in the region where corona occurs. It had the same drawbacks as capacitor life and capacity reduction.

On the other hand, it is possible to reduce the sheet resistance value of the metallized layers of both the two poles, but this has the disadvantage that the self-healing performance is poor due to the thicker metallized layers, and the initial capacitor withstand voltage is not satisfactory. It was also inappropriate.

Means for solving the problems The technical means of the present invention for solving the above problems are as follows:
The range of vapor deposited film resistance values of split electrodes and non-split electrodes is 2.0~
The difference is within the range of 6.0 Ω/hole, and the difference between the vapor deposited film resistance value of the divided electrode and the vapor deposited film resistance value of the non-divided electrode is 1.0 Ω/hole or more.

action The effect of this technical means is as follows.

That is, by providing a deposited film resistance value difference of 1.0 Ω/hole or more between both electrodes, the self-healing effect caused by minute partial discharge (corona) generated between the dielectric film layers can be
Since the metallized layer is thinner on the electrode side where the resistance value of the deposited film is higher,
The self-healing effect is more likely to occur, and the scattering area of the vapor deposited film is smaller than that of a vapor deposited film whose resistance value is around the same value, so the scattering energy during the self-healing effect is smaller, resulting in a shorter service life. The capacitance decrease during operation is small, making it possible to design a high potential gradient.

The larger the difference in resistance value of the deposited film between both electrodes is within the range of 2.0 to 6.0 Ω/hole, the more effective the capacitance is reduced.

Example An embodiment of the present invention will be described below based on experimental results.

First, in Fig. 1a, in order to confirm the scattering of the vapor deposited film during self-recovery due to the difference in resistance value of the vapor deposited film, the divided vapor deposition electrode 1 and the non-divided vapor deposition electrode 2 are connected so that there are no wrinkles between the copper electrodes 3. Install it so that a load of about 1oog/cIII is applied, and
This shows a test device in which the voltage of the C power source 4 is gradually increased to generate a self-recovery effect.

The graph in Figure 1 shows the results obtained using the above test device. As can be seen from FIG. 1, it can be seen that the scattering area of the deposited film becomes smaller when the resistance values of the deposited films are made to differ by about 1.0 Ω/hole or more. This phenomenon is
If a self-healing effect occurs due to the high film resistance and thin film thickness of one electrode, the deposited film is more likely to scatter on the thinner electrode, and at the same time, the electrical energy at the time of scattering is also lower. This shows that less is needed. This means that when both electrodes have the same film resistance value, when self-healing occurs, the deposited films on both electrodes have the same thickness, so the rate of scattering of the deposited films on both electrodes is high; Since the electric energy at the time is also large, the scattering area of the deposited film is also large as a result.

Further, the experimental results showed that even if the resistance value of the vapor deposited film was lowered for either the segmented vapor deposition electrode 1 or the non-segmented vapor deposition electrode 2, there was no significant difference in the experimental results between the two. However, the scattering area of the vapor deposited film tends to be smaller when the film resistance value of both electrodes is made different at a high value than when the film resistance value is made different at a low value. This means that since the film is thin, the electrical energy needed for self-recovery is small, and the scattering area is small.

Based on the above experimental results, a sample was actually prepared as a capacitor and a life test was conducted. The results are shown in FIG. A polypropylene film with a thickness of 8 μm and a single-sided aluminum vapor-deposited film was used as a sample.
The films constituting the divided electrodes as shown in the figure were stacked and wound to obtain a 30 μF capacitor element, and the end faces of the element were further sprayed with metal to take out the electrodes, which were then packaged with epoxy resin. The resistance value of the deposited film was prepared according to the value shown in FIG.

The life test conditions were an applied voltage of 520V and a temperature of 80'C.
I did it. As can be seen from the test results, the sample with a larger difference in vapor-deposited film resistance value had a capacitance change rate of Δc7c% in the life test.
is very small at about -1 to -2% at a life test time of about 1000 hours, whereas it is the same for products with small resistance value differences (about -5% at 1000 hours.Graph The reason why the capacitance change rate ΔC/C% is large at the early stage of the current application time for the sample with membrane resistance difference of 0.3Ω/hole in the case of the membrane resistance value 2.0Ω/hole and 2.3Ω/hole in 4 above is because of the membrane resistance. This is because the resistance value is low and the deposited film is thick, resulting in poor self-healing performance and low withstand voltage, which causes the dielectric in the sub-divided electrode to break down and activate the safety function.It is not shown in the test results on the graph. However, for samples with a difference in membrane resistance at membrane resistances of 5.0 Ω/hole or higher, when the membrane resistance exceeds 5.0 Ω/hole, the self-healing performance of the high-resistance electrode becomes acute, resulting in a change in capacitance. On the other hand, for samples with a membrane resistance value of 2.0 Ω/unit or less, the withstand voltage of the low-resistance electrode film decreases significantly when the membrane resistance value becomes 2.0 Ω/unit or less. In order to
As a result, the self-safety function operates, and the capacitance change rate increases significantly, making it impossible to satisfy JIS standards.

As mentioned above, the life test samples in the examples used a combination of single-sided vapor-deposited polypropylene films as dielectrics, but similarly, combinations of double-sided vapor-deposited films and non-evaporated films, or combinations of polyethylene terephthalate films, polyethylene terephthalate films, etc. A combination of terephthalate film and polypropylene film may also be used.
In any case, if the membrane resistance values of the two electrodes are within the range of 2.0 to 5.0 Ω/mouth and the difference in the membrane resistance values of the two electrodes is 1.0 Ω/mouth or more, the same life test results will be obtained.

Effects of the Invention As described above, the present invention has an aluminum vapor-deposited split electrode structure having a safety function whose vapor-deposited film resistance ranges from 2.0 to 5.0Ω/
To provide a metallized film capacitor that allows a stable high potential gradient design with very little capacity loss in a life test by setting the difference in resistance value of the deposited film between the two electrodes to 1.0Ω/mouth or more. It has great industrial value.

[Brief explanation of drawings]

Figure 1a is a perspective view of the main parts of a device that performs a test to confirm the scattering state of the deposited film during self-recovery of a capacitor, Figure 1 is a characteristic diagram showing the test results using the same device, and Figure 2 is a diagram of this book. FIG. 3, which is a time characteristic diagram of the capacitance change rate showing the life test results of the capacitor in the embodiment of the invention, is a partially exploded perspective view of a capacitor having a general split electrode structure and a safety function. 1... Capacitor element, 2... Divisionally deposited electrode film, 3... Division margin, 4...
. . . Deposited film removed portion (blank area), 6 . . . Non-divided evaporated electrode film. Name of agent: Patent attorney Toshio Nakao and one other person

Claims (1)

[Claims] Of the two vapor-deposited metal electrodes facing each other with a dielectric film in between, one is a split electrode divided into multiple pieces in the length direction of the film, and the split electrode is intermittently applied along the end of the electrode where the sprayed metal is applied. In a metallized film capacitor with a blank space for metal electrodes, the metal to be deposited is aluminum, and the resistance value of the two electrodes is set to 2.0 to 5.0Ω/hole, and the resistance value of the metallization film on the split electrode side is different from the resistance value of the metallized film on the split electrode side. A metallized film capacitor with a difference in vapor deposited film resistance on the side of the divided electrodes of 1.0Ω/port or more.